Today, carbon dioxide emissions from automobiles are required to be reduced. Since reduction of weight of vehicles greatly influences improvement of fuel efficiency, the weight of wire harnesses for connecting electrical components are also required to be reduced. Therefore, it has been studied to, for example, replace copper-based materials which are conventionally used for electric wires or the like used for the wire harnesses with aluminum, and aluminum has been used for some electric wires.
However, an electrical structural body including an aluminum wire pressure-bonded to a crimp terminal has a problem that aluminum having a low potential is corroded as a result of contacting a metal material having a high potential, such as tin or gold used to plate the terminal, or such as a copper alloy used for forming the terminal; namely, has a problem of galvanic corrosion.
The above-mentioned galvanic corrosion is a phenomenon that when water is attached to a site at which a metal material having a high potential and a metal material having a low potential contact each other, a corrosion current is generated, and as a result, the metal material having a low potential is, for example, corroded, dissolved, or extinguished. In the case of a connection structural body mentioned above, the aluminum wire pressure-bonded to a pressure-bonding section of the terminal is corroded, dissolved, or extinguished, and thus the electric resistance is raised. This causes a problem that the connection structural body cannot exhibit a sufficient conducting function.
According to a technology which is proposed to prevent the galvanic corrosion of such an aluminum wire used in a connection structural body, a main body of the crimp terminal is formed of an aluminum material and an elastic piece for supporting a contact of the crimp terminal, which is to be in contact with a connection terminal used for electrical connection, is formed of an iron-based material (see Patent Document 1). It is described that this can prevent the galvanic corrosion of the aluminum wire.
However, the technology described in Patent Document 1 is difficult to be applied to the conventional processing procedure for producing a terminal, namely, a continuous procedure of punching out the material of the terminal with a press and bending the material. Thus, it is difficult to mass-produce the terminal with the technology described in Patent Document 1. In addition, the technology described in Patent Document has a problem that galvanic corrosion occurs due to the material used to form the elastic piece and aluminum used to form the main body of the terminal.
According to another proposal to prevent the galvanic corrosion of the aluminum wire, core wires exposed from an end of the electric wire is covered with an intermediate gap to conduct and thus connect the core wires and the intermediate gap to each other, and also the intermediate cap and a metal fitting of the terminal are conducted and thus connected to each other, so that the electric wire and the metal fitting of the terminal are conducted and connected to each other (see Patent Document 2).
Patent Document 2 describes as follows: although the electric wire and the intermediate cap formed of different metal materials contact each other, the contact site is not exposed owing to the above-described structure; and as a result, water is not attached to the contact site and thus galvanic corrosion is not caused. It is expected based on this structure that the galvanic corrosion can be also prevented by applying an organic material such as a grease or a resin to an exposed part of the aluminum wire in the connection structural body.
However, the proposal described in Patent Document 2 complicates the structure for pressure-bonding the electric wire. Therefore, it is difficult to optimize the pressure-bonding conditions, namely, the caulking conditions. In addition, the proposal described in Patent Document 2 has a problem that a tiny gap or the like is made, and thus galvanic corrosion advances rapidly, which makes it difficult to maintain the conducting function.
In the case where an organic material such as a grease or a resin is applied to the exposed part of the electric wire as described above, it is not easy to apply such a gris, resin, etc. to a pressure-bonding section having a complicated structure in a highly airtight state for the purpose of, for example, guarantee durability of an automobile against long-time use. There is a risk that, for example, galvanic corrosion proceeds rapidly from a gap such as a crack or the like made as a result of long-time use.